(1) Field of the Invention
This invention relates to a tool for rotating a threaded fastener comprising a wrench head, a drive member arranged for rotation therein and for direct or indirect engagement with the fastener, an elongate member reciprocally mounted in the head and arranged such that movement thereof in one direction causes rotation of the drive member to enable the fastener to be rotated quickly with low torque and locking means for locking the head to the drive member to allow a high torque to be applied thereto through a relatively small angle for final tightening or initial loosening of the fastener.
(2) Description of the Prior Art
Two-speed wrenches make it possible to rotate the rotatable member of a threaded fastener, such as a nut, bolt or screw, at a relatively high speed when loose, and for a high torque to be applied through a small angle for the final tightening or for starting a fastener which is to be undone. The simplest form of two-speed tool is a pivotal handle which can be used with the two parts aligned in order to rotate loose fasteners, rather in the manner of a screw-driver, and with the parts at right angles to apply a high torque. A two-speed ratchet wrench is known from U.S. Pat. No 735,134 in which the inner end of the elongate member is engageable with ratchet teeth on the drive member and is manually reciprocable by means of an integral finger extending outside the wrench head and terminating in a knob which is grasped by the operator. Such an arrangement is fiddly to use and demands a great number of manual movements to rotate the fastener through a few revolutions. In the preferred embodiment described in this U.S. Specification the rotation of the drive member independently of the wrench head for the relatively high-speed rotation of loose fasteners is effected by the rotation of a shaft journalled longitudinally in the wrench handle and having at its inner end a pinion engaging gear teeth formed on the drive member, and at its outer end a handle for rotating the shaft, which is axially slidable so as to be used in the normal way for final tightening or initial loosening of the fastener.
More sophisticated forms of this type of two-speed ratchet wrench are disclosed in U.S. Pat. No 2,703,030 in which, in some embodiments, the shaft is axially slidable so as to disengage the gears; and in UK No 2,004,794 in which the axial movement of the shaft is additionally utilised to move the ratchet pawl between two engagement positions for drive in opposite senses and a central, disengaged position. However all these wrenches require the turning of a rather small handle at the distal end of the wrench handle itself which is a somewhat fiddly, and often inconvenient, operation. The above mentioned U.S. No 2,703,030 and UK No 300,713 disclose the use of a power source to rotate the shaft.
The development of two-speed wrenches has thus been in the direction of effecting high speed rotation by providing a shaft in the handle which demands either fiddly manual rotation or expensive powered rotation.